We propose to develop a non-cryogenic ultra-low-field (ULF) magnetic resonance imaging (MRI) system based on an atomic magnetometer (AM) for general biomedical imaging and demonstrate the first anatomical in vivo images of the hand and the head. The system will have several advantages over conventional high-field scanners: safety, portability, low cost, compatibility with other systems, flexibility in applications, simplicity in operation, enhanced contrast (to anomalies such as tumors). In many cases, this will be a benefit to MRI diagnostics when conventional MRI scanners are restricted. For example, the proposed system can be deployed in remote (rural) areas of the US, small hospitals, battlefields, and hospitals in undeveloped countries, where logistically and economically conventional scanners cannot be used. Because of the absence of cryogenics, maintenance-free operation, and cost reduction, the proposed system also has an advantage over ULF MRI systems based on SQUIDs, which have already been used successfully by our group and others in biomedical applications. Significant cost reduction can be achieved for the system utilizing parallel MRI principles, desirable for accelerating MRI scans, because a multi-channel AM can be built at a fraction of the cost of the multi-channel SQUID array (40k$ vs 1000k$). If we obtain the quality of in vivo scans suitable for most common diagnostic MRI procedures, which is our ultimate goal, the ULF MRI scanners based on atomic magnetometers can revolutionize MRI technology. Detailed proof of the feasibility, including preliminary results and the detailed description of the principles and optimization steps, is provided. PUBLIC HEALTH RELEVANCE: We propose to develop a non-cryogenic ultra-low-field (ULF) magnetic resonance imaging (MRI) system based on an atomic magnetometer (AM) for general biomedical imaging and demonstrate the first anatomical in vivo images of the hand and the head. The system will have several advantages over conventional high-field scanners such as safety, portability, low cost, compatibility with other systems, flexibility in applications, simplicity in operation, and enhanced contrast (to anomalies such as tumors), as well as the advantage over ULF MRI systems based on SQUIDs such as the absence of cryogenics, maintenance-free operation, and low cost. If we succeed in obtaining the quality of in vivo scans suitable for most common diagnostic MRI procedures, and preliminary results and analysis in this proposal prove the feasibility of this, the ULF MRI scanners based on atomic magnetometers can become reality in medical hospitals and revolutionize MRI diagnostics.